<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    * {
      padding: 0;
      margin: 0;
    }

    ul {
      list-style: none;
    }

    .tabBox {
      box-sizing: border-box;
      width: 600px;
      margin: 20px auto;
      /* border:1px solid red; */
    }

    .tabBox .tab {
      display: flex;
      position: relative;
      top: 1px;
    }

    .tabBox .tab li {
      border: 1px solid black;
      margin-right: 10px;
      line-height: 30px;
      width: 100px;
      padding: 5px;
      text-align: center;
    }

    .tabBox .tab li.active {
      border-bottom: 1px solid aliceblue;
    }

    .tabBox .content {
      width: 600px;
      height: 400px;
      border: 1px solid black;
      box-sizing: border-box;
      text-align: center;
      line-height: 400px;
      display: block;
    }


  </style>
</head>

<body>
  <div id="app">
    <div class="tabBox">
      <ul class="tab">
        <li :class="{active:index === curIndex}" v-for="(item, index) in ary" @click="fn(index)">{{item.name}}</li>
      </ul>

      <div :class="{content:true}">{{content}}</div>
    </div>
  </div>
  <script src="../node_modules/vue/dist/vue.js"></script>
  <script>
    let ary = [
      {
        id: 1,
        name: '一',
        value: '我是第一个'
      },
      {
        id: 2,
        name: '二',
        value: '我是第二个'
      },
      {
        id: 3,
        name: '三',
        value: '我是第三个'
      }
    ]
    let vm = new Vue({
      el: '#app',
      data: {
        ary,
        curIndex: 0,
        content:''
      },
      created(){
          this.content = this.ary[this.curIndex].value;
      },
      methods: {
        fn(index) {
          this.curIndex = index;
        }
      },
      computed:{
        // content(){
        //   return this.ary[this.curIndex].value;
        // }
      },
      watch:{
        curIndex(){
          this.content = this.ary[this.curIndex].value;
        }
      }

    })


  </script>
</body>

</html>